In order to measure the state of charge of primary batteries, it is usually necessary to measure the current or voltage of the battery under test. The testing of current and voltage is usually performed with external test equipment, such as voltmeters and battery testers. The cost of the associated test equipment or testers varies widely. There are digital multimeters which will measure both voltage and current as well as devices which utilize simple resistor calibrated galvometers. There is also heat sensing material which changes color when the material is heated up by an electrical conductor which is placed across the battery terminals. In all cases of the measurement of a primary battery, it has been necessary to place the battery either in or near the tester and then to initiate the test. In some tester devices, the placing of the battery in the tester itself causes electrical contact to be made with the battery which initiates the test. In other cases, external leads from the tester are connected to the battery terminals to initiate the test. In some cases, the state of charge reading is monitored continuously by the test device, but in most cases it is done briefly in order to provide a quick sampling of the state of charge of the battery.
The principal problem with all of these methods is that an external tester of some kind must be used to measure the state of charge of primary batteries. The battery alone will not render any state of charge information to the user.
In accordance with the disclosure of U.S. patent application Ser. No. 760,200, filed Sep. 16, 1991, in the names of William Bohmer and Clark F. Bow, William Bohmer being the sole applicant herein, there is provided a battery charge indicator which is comprised of a first means to define a compressible chamber for containing a viscous gel and having an outlet therefrom as well as a second means to define a viewing channel of predetermined shape in communication with the outlet of the chamber in order to receive a flow of gel therefrom in an amount corresponding to a predetermined compression of the chamber. The battery charge indicator is incorporated into the battery, such as an alkaline battery, including a housing having an internally contained chemical cathode and anode for generating an electrical current with the cathode expanding in an amount proportional to the total current generated. The battery charge indicator is incorporated in the alkaline battery in such a manner that the compressible chamber is exposed to the cathode for compression thereby in response to an expansion of the cathode.
The cooperation between the battery charge indicator and the alkaline battery is such that when there is an electrical discharge from the battery, the internal components of the battery expand accumulatively as the battery discharges, thereby producing a force which can be used to operate the built-in battery charge indicator in order to indicate the enclosed expansion which is inversely proportional to the remaining electrical charge in the battery. Thus this battery charge indicator operates mechanically to amplify the expansion of the cathode in order to render a continuous sensitive visual state of charge indication. This battery charge indicator is typically installed at one end of the battery as a permanent part of the finished product. Further, this battery charge indicator is constructed in order to produce a visual indication of the state of charge in an analog manner.
In one construction of this battery charge indicator of application Ser. No. 760,200, the means for defining a compressible chamber is formed by a cap having a flexible section and a disk disposed on the cap in order to define the compressible chamber therebetween. In this construction, an outlet is disposed centrally of the disk in order to permit a viscous gel to be expelled from the chamber proportionally in response to the compression of the chamber caused by the expansion of the cathode of the battery. In this construction, the means defining the viewing channel may be in the form of a second disk which is mounted over the disk which forms the compressible chamber. Further, this second disk may have the viewing channel formed therein, for example, in the shape of a radially disposed section which extends from the outlet of the compressible chamber and a circular section which extends from an outer end of the radially disposed section. The viewing channel may also terminate in a reservoir located at one end of the circular section of the channel.
A cover is also disposed over the viewing channel of the battery charge indicator, which for example, may be a positive cover for the battery. In addition, the cover has a plurality of spaced apart apertures overlying the viewing channel in order to permit viewing thereof. Thus, as the gel is extruded into the viewing channel in response to the compression of the compressible chamber, the extent of the gel within the channel can be viewed. As the extent of extrusion provides an indication of the remaining charge in the battery, a simple visual indication of the remaining life of the battery is provided.
In another construction of the battery charge indicator of application Ser. No. 760,200, the compressible chamber for the gel is formed by a closed flexible end of the battery housing and a disk which is disposed over the closed flexible end of the housing. This disk is provided with an outlet into a viewing channel within an overlying second disk which is held over the end of the battery housing, for example, by means of a positive cover having apertures for viewing of the channel.
In still another construction of the battery charge indicator of application Ser. No. 760,200, the compressible chamber of the battery charge indicator may be in the form of a flexible tube of elongated shape which is disposed within the battery housing by being passed through an opening in a closed end of the housing. This tube is also provided with an outlet at one end for the gel as well as an overlying disk having a viewing channel therein for receiving the gel extruded from the flexible tube. In order to enable viewing of the gel within the viewing channels of the various embodiments, the disk in which the channel is formed may be made of transparent or translucent material.
In a further construction of the battery charge indicator of application Ser. No. 760,200, the alkaline battery is constructed of a housing having a closed end wall and a deformable wall against which the cathode expands when electrical current is being generated. In addition, a piston assembly is disposed in contact with the deformable end wall for movement therewith while a means is provided for measuring the amount of movement of the piston assembly in order to provide a visual indication of the remaining amount of the expected expansion of the cathode. The piston assembly may be constructed to include a guide pin which is disposed in contact and which extends longitudinally from the deformable end wall of the housing and an annular disk mounted on the pin for movement therewith. In this case, the means for measuring the movement of the piston assembly includes a reflector having a central bore slidably receiving the disk, a lens for viewing a reflection of a side face of the disk from the reflector, and a cover having at least one aperture overlying the lens for viewing the reflection. The disk is provided with a flat peripheral wall which is provided with an indicia to provide a visual reflected image corresponding to the remaining amount of expected expansion of the cathode, that is, the remaining amount of charge. The indicia may be in the form of a band of color or multiple bands of different color.
In use, as the battery discharges, the deformable and of the battery will expand outwardly thus causing the piston assembly to move outwardly of the housing. By means of the lens and reflector, the peripheral wall of the disk of the piston assembly can come into view with the band of color on the wall providing a measure of the amount of movement of the piston and, thus, the remaining amount of charge.